In the electronics industry, the tendency has been to reduce the size of electronic devices such as camcorders and portable telephones while increasing performance and speed. Integrated circuit packages for complex systems typically are comprised of multiple interconnected integrated circuit chips. The integrated circuit chips usually are made from a semiconductor material such as silicon or gallium arsenide. The integrated circuit chips may be mounted in packages that are then mounted on printed wiring boards.
Typically, the packages on which these integrated semiconductor chips are mounted include a substrate or other chip-mounting device. One example of such a substrate is a leadframe. Leadframes typically include an area on which an integrated circuit chip is mounted and multiple power, ground, and/or signal leads to which power, ground, and/or signal sites of the integrated semiconductor chip are electronically attached. Semiconductor integrated chips may be attached to the leadframe using adhesive or any other techniques for attaching such chips to a leadframe which are commonly known to those skilled in the art. The power, ground and/or signal sites on the chip may then be electrically connected to individual leads of the leadframe through techniques such as wire bonding.
A conventional leadframe includes a die pad, surrounded by a number of leads. Usually the leadframe is made from metal. In order for the leadframe to be handled as a single piece of substrate, connection elements are used to connect different parts of the leadframe together. The leads are usually connected by the outer frame of the leadframe. A tiebar usually connects the die pad to the outer frame of the leadframe. The connection elements are usually made out of the same metal as the leadframe due to the fact that the entire leadframe structure, including the connection elements, is cut out from a single piece of metal plate during a metallurgical forming process.
The trend of the modern semiconductor industry is to integrate more and more functionally into one package. This trend requires an ever increasing number of leads to be present in the leadframe. One way of increasing the lead count of the leadframe is to form leads extending from the periphery of the die pad.
The packaging process starts with attaching an integrated circuit chip to the die pad using a conductive adhesive such as silver epoxy. The conductive adhesive is cured after the die attach. Then a wire bonding process is typically used to make electrical interconnections between the integrated circuit and the leads of the leadframe. After wire bonding, the leadframe with the integrated circuit attached is encapsulated using a mold compound.
That the leadframe after the stage of molding is still a single piece of connected metal suggests that all the leads are shorted together. A singulation process is used to cut the outer frame of the leadframe and thus separates the leads connected by the outer frame as well as separates individual semiconductor package apart. However, the leads that extend from the die pad are still shorted together and not separated. Usually a partial sawing process is employed to separate those leads. However, this partial sawing process creates certain problems because it makes the manufacturing process more complicated, it creates moisture pathway that introduces water moisture into the package that leads to device failures, it creates mechanical cracks in the package that leads to device failures, and it might cut too deep and damage other components of the package. Another problem with the partial sawing is that such a process prevents a more versatile lead layout from being realized. Usually there is only one row of leads extending from the die pad. If two rows of leads are desired, two steps of partial sawing would be required to separate them and the risks mentioned above associated with such partial sawing increase dramatically.
Thus, a need still remains for increasing the lead or pin count, providing a more versatile lead layout scheme, eliminating the partial sawing that introduces risks, and simplifying the manufacturing process for an integrated circuit package. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.